Samsung is testing massive 18,000 mAh silicon smartphone batteries, leaked documents reveal

The successor to the Samsung Galaxy S26 Ultra (starting at $1,300 on Amazon) could feature a significantly larger battery. Leaker @phonefuturist obtained documents indicating that Samsung is currently testing multiple silicon-carbon batteries. The largest among the test units is reportedly a massive 20,000 mAh battery, though it developed a defect after just 960 charge cycles.

Samsung is apparently also testing an 18,000 mAh battery comprising three stacked cells. It combines a 6,699 mAh cell (4.2 mm), a 6,000 mAh cell (3.9 mm), and a 5,527 mAh cell (3.28 mm) for an overall thickness of 12.8 mm, making it better suited to relatively thick outdoor smartphones. At 9.3 mm thick, the 12,000 mAh battery consisting of two cells may be a slightly more viable option for mainstream phones.

Samsung expects this battery to last 1,500 charge cycles before its capacity drops to 80%. The 12,000 mAh capacity should be enough to provide 20 to 25 hours of active use in a smartphone. Since the battery runtime and life-cycle tests are still ongoing, these figures remain theoretical. Although these batteries are too thick for most Samsung Galaxy phones, the leaked documents show that Samsung is actively developing silicon-carbon batteries, suggesting the company could in the future offer devices with battery capacities comparable to competing models from China.